“Grounding” is the art of making an electrical connection to the earth. This ground connection may actually be the interface with earth, and through that interface, the grounded system may be in electrical contact with the whole earth. Through that interface may pass electrical “events” to and from the connected system(s). These electrical “events” may include power from the utility, communications, phone, radio, and other forms of data, among others.
The character of this interface may determine the effectiveness of its function, i.e., how “good” is the interface and/or is there a reliable, year-round connection to earth. The effectiveness of an interface may be assessed in terms of its true DC resistance to Mother Earth. However, there may be another factor of greater concern, that is, the transient response or surge impedance, or the effective inductance of that interface. This factor will determine the effectiveness of that interface for such functions as lightning grounds, RF grounds, electric utility protection equipment grounds, and personnel safety under “ground faulting” conditions.
The earth interface system is an important subsystem. The blind application of standards with little reference to the site character or the effect of seasonal changes may not yield an effective ground interface.
When the earth interface system has not been properly engineered, significant system equipment damage may persist, personnel safety may be impaired, and system performance may be less than ideal.
Finally, the trend toward microelectronics may make electrical and electronic systems even more sensitive to any form of anomalous electrical transients. Grounding the earth interface must now be considered a vital function and must be engineered for each site and/or system individually.
Grounding systems perform at least one of the following functions:
1. A Ground, or Earth Reference Electrode.
Every electrical or electronic system must be referenced to the earth. This is referred to as “grounding.” The grounding point in that system provides a common reference point for circuits within the system. In many cases, the resistance to earth of that reference point may be of little significance. For these systems a Common Point Ground (CPG) may satisfy the functional requirements. These systems may be totally self-contained or autonomously operated systems, requiring little or no external interfaces, and may present little or no potential for a compromise of personal safety. This form of grounding system, the CPG, mandates a separate connection from each element in the system to that CPG, preferably via a separate path. A simple example of this CPG is a single computer terminal where the green wire in the power plug is the ground reference.
2. The Lightning Neutralization Ground.
Lightning protection grounding system requirements have conventionally been thought to be similar to the preceding ground reference, however, they may be quite different. A more descriptive title would be: “Lightning Charge Neutralization System”. This may come about because of the nature of atmospheric electricity and the lightning strike mechanism. Storm clouds induce an image charge of equal, but opposite potential, in the earth beneath the cloud. When a lightning channel terminates on an earthen object, that channel forms a conductive path between the two bodies to permit equalization of the charge between them. Since the charge is induced on the surface of the earth, it follows that all of that charge must move from where it was induced, to a strike channel terminus, in order to neutralize the charge between earth and that cloud. All this may happen in approximately 20 microseconds or so. If a facility to be protected from damage from a lightning strike is part of the charged body or is the terminus of the strike, its grounding system must provide a low resistance, low surge impedance path from any point in the system to any other point in the system where the strike may terminate. Therefore, the grounding requirement for lightning protection may not just be a low DC resistance to ground, but may be an interconnecting ground network that electrically interconnects every vulnerable component of the plant or system of concern with a low surge impedance path.
3. A Universal System.
The universal grounding system may require a near perfect interface with the earth. That is, the lower the effective resistance between that system ground point and true earth, the better, safer, or more effective the system may be. This requirement may be usually associated with systems that have many interfaces with other systems, or the “outside world.” Typical examples may include the electrical utility industry, the telephone central office and large industrial plants, among others. These same systems may require a common point grounding (CPG), a lightning neutralization capability, and a low impedance interface with earth; thus providing a universal grounding (or earth) interface.
Some grounding drive rods come in various lengths, such as 8′, 10′, and 20′, with the 10′ lengths being the most common. They may be installed by being pounded into the ground using anything from a sledgehammer to a jackhammer. A standard driven rod may look like a giant nail, pointed at the tip, with the remainder being a smooth shaft. There may be no top piece of metal for hammering similar to that of a nail.
Some standard driven rods may work well if the soil is soft and moist, however. If the soil is hardpan or rocky, or if other impediments are within the soil, a standard driven rod may not work well for a number of reasons. First, when pounding a standard driven rod into the ground, and a rock or an obstruction is encountered, a standard rod may bend or break trying to get around the obstruction. Furthermore, there may be rod refusal, which means no matter how much force is applied, it may be impossible to drive a standard rod any further onto the soil.
This may be of concern when driving standard rods that are longer than 10′. In order to have a standard driven rod longer than 10′, two standard 10′ rods may be coupled together to achieve the desired length. Many standard rods may be connected together using a coupler that may be larger in diameter than the diameter of the rod. This may mean that if the ground rod is ⅝″, the coupler may be ¾″ in diameter, which may make it more difficult to drive the ground rod into the soil. This added diameter may make the rod almost impossible to drive into the earth. This may also compound problems, as codes and/or regulations may require that there be a minimum of 8′ of ground rod in the ground, or sometimes as much as 10′ or 20′ to meet certain grounding requirements.
If this occurs, the only options may be to cut off the rod, cover it up and start again, or try to find an alternative way to drive the rod past the hard-pan soil or obstruction. This process may be very labor intensive and time consuming, and may add to the material costs needed. Unfortunately, a contractor installing the ground rods may have no choice; as the rod may have to be driven to meet the requirements set forth by design, city, state, or federal regulations and/or codes.
In soils such as, but not limited to permafrost and the like, ground rods may be pushed out of the soil and/or may be very difficult to install. Furthermore, to meet codes and other requirements, standard ground rods may have to be coupled together, then cut off to achieve the proper resistance to ground.
What is needed is a versatile grounding system that may be relatively easy to ship, install, and use. Furthermore, what is needed is a grounding system that may enhance the electrical properties of the system, may be configured to be installed in soil with impediments, and may be more likely to remain in the soil during changing soil conditions.